All-Oxide MoOx/SnOx Charge Recombination Interconnects for Inverted Organic Tandem Solar Cells

Tim Becker, Sara Trost, Andreas Behrendt, Ivan Shutsko, Andreas Polywka, Patrick Görrn, Philip Reckers, Chittaranjan Das, Thomas Mayer, Dario Di Carlo Rasi, Koen H. Hendriks, Martijn M. Wienk, René A. J. Janssen, Thomas Riedl

Index: 10.1002/aenm.201702533

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Abstract

Abstract Multijunction solar cells are designed to improve the overlap with the solar spectrum and to minimize losses due to thermalization. Aside from the optimum choice of photoactive materials for the respective sub-cells, a proper interconnect is essential. This study demonstrates a novel all-oxide interconnect based on the interface of the high-work-function (WF) metal oxide MoOx and low-WF tin oxide (SnOx). In contrast to typical p-/n-type tunnel junctions, both the oxides are n-type semiconductors with a WF of 5.2 and 4.2 eV, respectively. It is demonstrated that the electronic line-up at the interface of MoOx and SnOx comprises a large intrinsic interface dipole (≈0.8 eV), which is key to afford ideal alignment of the conduction band of MoOx and SnOx, without the requirement of an additional metal or organic dipole layer. The presented MoOx/SnOx interconnect allows for the ideal (loss-free) addition of the open circuit voltages of the two sub-cells. A novel all-oxide recombination interconnect for organic tandem solar cells is reported. A large interface dipole between the high-work-function (WF) metal oxide MoOx and low-WF tin oxide (SnOx) affords ideal alignment of the conduction band of the two n-type metal oxides. The actual recombination of electrons with holes occurs at the interface of organic/MoOx of the lower sub-cell.